The present invention relates to an absorbent composite, and in particular, an absorbent composite with an absorbent layer comprising micro-fibrillated cellulose-coated super absorbent polymer. The present invention also relates to a method of making the absorbent composite and to disposable absorbent articles employing absorbent composite. Disposable absorbent articles include diapers, youth pants, training pants, adult incontinence products, bodily exudates absorbing products, feminine hygiene products, and other absorbent products (collectively “disposable absorbent articles”).
Prior disposable absorbent articles typically employ three basic structural elements: a topsheet that forms the inner surface, a backsheet that forms the outer surface, and an absorbent core that is interposed between the top sheet and the backsheet. The topsheet is designed to allow liquid to pass from outside the absorbent article through the topsheet and into the absorbent core. The topsheet may be made out of a range of liquid and vapor permeable hydrophilic or hydrophobic materials. The permeability of the topsheet can be increased by using surface activation agents (“surfactants”). Surfactants lower the surface energy or the contact angle of the liquid-solid interface and facilitate the liquid's passage through the top sheet.
The backsheet is designed to prevent fluid from passing from the absorbent core through the backsheet and out of the absorbent article. The backsheet may be made out of an impermeable film that extends the full width of the article or a combination of cloth-like material and impermeable film. The backsheet may also have vapor transmission properties (“breathability”) that allow vapor to pass through the backsheet without releasing fluid stored in the absorbent core. The backsheet may also be made from a liquid impermeable but vapor transmittable non-woven material such as spun-bond, melt-blow, spun-bond (“SMS”); spun-bond, melt-blown, melt-blown, spun-bond (“SMMS”); micro, nano, or splitable fibers; spun melt or spun laced; carded; and the like.
The absorbent core is designed to contain and distribute fluid that passes through the topsheet. A typical absorbent core is made out of a high or super absorbent polymer (SAP) stabilized by an absorbent matrix. SAP is commonly made out of materials such as polyvinyl alcohol, polyacrylates, various grafted starches, and cross-linked sodium polyacrylate. SAP can be in the form of particles, fibers, foams, web, spheres, agglomerates of regular or irregular shapes, and film. The absorbent matrix is typically a de-fiberized wood pulp or similar material. The absorbent matrix is very bulky relative to the topsheet, backsheet, and SAP. Traditionally, most of a diaper's thickness has come from the absorbent core.
Increasingly, consumers of absorbent articles are demanding thinner absorbent articles. To meet these demands, manufacturers are decreasing the thickness of absorbent articles by decreasing the amount of absorbent matrix used in absorbent cores. Although the resulting absorbent cores are thinner, they suffer in performance. As the amount of absorbent matrix is reduced, it is less effective in stabilizing the SAP-preventing the SAP from migrating within the absorbent core. As SAP migrates within the core, the absorbent core loses its effectiveness and no longer has uniform absorbency. For example, SAP that is not contained tends to collect in wetted areas and is inefficient for handling subsequent discharges.
Manufactures have attempted to solve this problem by creating small, individual SAP pockets or by gluing the SAP. These solutions, however, have been largely unsuccessful. The SAP pockets merely limit the migration to movement within the pockets. However, because there is still movement of the particles, the absorbent core does not exhibit uniform absorbency. Gluing stabilizes the SAP, but results in an uncomfortably stiff absorbent core and a loss in the SAP's swelling capacity.
Accordingly, there exists a need for an improved absorbent product that continues the trend of decreasing product thickness, while minimizing product stiffness and exhibiting excellent absorbency.